Gas Sorption Tester For Rapid Screening of Multiple Samples

ABSTRACT

An apparatus determines gas sorption properties of a large number of material samples simultaneously. The apparatus includes a switchable manifold of low-volume conduits and an array of sensors, where each low-volume conduit fluidly couples a single sample of gas-sorbing material to a dedicated detector. The switchable manifold is also configured to fluidly couple the samples to a vacuum source or a dosing gas source. Because of the very low internal volume of the conduits, essentially all gas released from a particular sample is accurately detected by the corresponding detector, either through sorption of the released gas, by measuring pressure, or by other means. In this way, a very accurate measurement of the quantity of gas released by the sample is made. In one embodiment, the array of sensors includes hydride-based sensors, which contain a material that forms an optically and/or electrically responsive hydride upon exposure to hydrogen-containing gas.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority benefit of the U.S. ProvisionalPatent Application titled, “METHODS AND APPARATUS FOR COMBINATORIALDETERMINATION OF SORPTION PROPERTIES,” filed on Sep. 18, 2007 and havingSer. No. 60/973,248. The subject matter of this related application ishereby incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate generally to devices forperforming measurements on small quantities of gases or liquids, andparticularly to an apparatus for performing gas sorption measurements onmultiple samples of gas-sorbing materials.

2. Description of the Related Art

Synthesis of materials using combinatorial chemistry has been usedeffectively to produce new materials having small variations incomposition and/or structure numbering in the 10s, 100s or 1000s at atime. Such materials processing methods have led to the discovery of newand improved chemicals, pharmaceuticals, semiconductor materials anddevices. However, due to the large numbers of different materialsinvolved, combinatorial methods can only lead to timely materialdiscovery when rapid screening of the physical characteristics of themany types of new materials produced thereby is available.

In the case of gas sorption materials, the gas sorption properties ofeach new material must be tested, i.e., the absorption, adsorption,desorption, physisorption, and/or chemisorption properties, and suchtesting for even a single sample is a lengthy and labor-intensiveprocess. Such tests include establishingpressure-composition-temperature (PCT) curves for materials, andperforming isothermal kinetics and capacity measurements, thermodynamicmeasurements (van't Hoff curves) and temperature-programmed desorption(TPD) measurements.

The sorption tests for establishing each PCT curve are time-consumingand require very sensitive instrumentation, such as high-accuracypressure transducers. In addition, collecting information regarding thekinetic sorption properties and thermodynamic stability of gas-sorbingmaterials typically requires further time-consuming testing of eachsample. Thus, characterizing the sorption properties of a new materialis a relatively expensive and lengthy process, especially since currenttesting techniques do not allow rapid screening or testing acrossmultiple samples. In light of the expanding need for characterizinglarge numbers of new materials, current techniques simply cannot be usedto efficiently or cost effectively analyze the large numbers ofdifferent materials to be tested, particularly those developed usingcombinatorial techniques.

Accordingly, there is a need in the art for an apparatus and techniquefor the rapid screening of multiple gas-sorbing samples.

SUMMARY OF THE INVENTION

One embodiment of the present invention sets forth an apparatus that candetermine the gas sorption properties of a large number of materialsamples simultaneously. The apparatus includes a switchable manifoldconfigured to fluidly couple an array of sensors and an array of samplesto a vacuum source, a dosing gas source, and each other. The array ofsensors may include pressure transducers, conventional gas detectors,resistivity sensors, and hydrogen-induced phase-change materialsincluding hydride-based sensors.

One advantage of the disclosed apparatus is that can be used toefficiently determine gas sorption properties of a large number ofmaterial samples simultaneously and with high accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a schematic diagram of a gas sorption apparatus configured toperform tests on multiple samples simultaneously, according to anembodiment of the invention.

FIGS. 2A-G schematically illustrate different operations performed by agas sorption apparatus in the course of sorption testing, according toembodiments of the invention.

FIG. 3 is a schematic illustration of a sample library, according to anembodiment of the invention.

FIGS. 4A, B illustrate schematic side views of one embodiment of theisolation of each sample area of a sample library from adjacent sampleareas.

FIG. 5 is a schematic side view of a sensor array containing anelectrically responsive material, according to an embodiment of theinvention.

FIG. 6 is a schematic side view of a sensor array containing anoptically responsive material, according to an embodiment of theinvention.

FIG. 7 is a schematic side view of another embodiment of a sensor thatincludes an optically responsive material and may be contained in asensor array.

FIG. 8 illustrates a schematic top view of a sensor array containing aplurality of sensors after sorption testing.

For clarity, identical reference numbers have been used, whereapplicable, to designate identical elements that are common betweenfigures. It is contemplated that features of one embodiment may beincorporated in other embodiments without further recitation.

DETAILED DESCRIPTION

Embodiments of the invention contemplate an apparatus that determinesgas sorption properties of a large number of material samplessimultaneously. The apparatus includes a switchable manifold oflow-volume conduits and an array of sensors, where each low-volumeconduit fluidly couples a single sample of gas-sorbing material to adedicated detector. The switchable manifold is also configured tofluidly couple the samples and/or sensors to a vacuum source and adosing gas source. Because of the very low internal volume of theconduits, essentially all gas released from a particular sample isaccurately detected by the corresponding detector, either throughsorption of the released gas, by measuring pressure, or by other means.In this way, a very accurate measurement of the quantity of gas releasedby the sample is made. Alternatively, essentially all of the gas in thevery low internal volume of the conduits may be absorbed by the sample,the quantity of gas adsorbed or absorbed being measured by thecorresponding detector, either through sorption of the released gas, bymeasuring pressure, or by other means. In one embodiment, the array ofsensors includes hydride-based sensors, which contain a material thatforms an optically and/or electrically responsive hydride upon exposureto hydrogen-containing gas.

FIG. 1 is a schematic diagram of a gas sorption apparatus 100 configuredto perform tests on multiple samples simultaneously, according to anembodiment of the invention. The principle components of gas sorptionapparatus 100 include a switchable manifold 101, an array 102 of sensors102A-D, a plurality of samples 103A-D, a dosing gas source 104 and avacuum source 105. For improved performance, gas sorption apparatus 100may also include a controller 110 coupled to a valve controller 111, apressure controller 112, a temperature controller 113, a heater assembly115, and a data collection system 114. Controller 110 is an electroniccontroller, such as a microprocessor, and is configured to control theoperation of gas sorption apparatus 100, e.g., valve operation, pressurecontrol, vacuum control, electronic data collection, temperature controland/or dosing quantity and frequency.

Switchable manifold 101 is configured to fluidly couple samples 103A-Dto detectors 102A-D by means of a low volume path. To that end,switchable manifold 101 includes low-volume conduits 106. For improvedaccuracy of gas sorption tests performed by gas sorption apparatus 100,the internal volume of low-volume conduits 106 is advantageouslyminimized. In one embodiment, low-volume conduits 106 comprisesmall-diameter electro-polished stainless steel tubing, having aninternal diameter of 2 mm or less. In an alternative embodiment,low-volume conduits 106 may be small-diameter holes formed through thebody of switchable manifold 101, e.g., by laser drilling, chemicalgrowth, chemical etching, or other techniques. In such an embodiment,low-volume conduits 106 may have outer diameters as small as 1 micron.Thus, the total free volume between a given sample and correspondingsensor may be 0.1 ml or less.

The material in which low-volume conduits 106 are formed preferably ischaracterized by low gas-permeability and out-gassing, such as stainlesssteel, glass, ceramic materials, alumina, Macor™, and other ultra-highvacuum (UHV) compatible materials. In one embodiment, low-volumeconduits 106 may be configured to thermally isolate sensors 102A-D fromsamples 103A-D, so that each sensor may be maintained at a substantiallydifferent temperature than its corresponding sample. For example,low-volume conduits 106 may be formed from small-diameter tubing thatconduct very little heat. Alternatively, low-volume conduits may bedrilled or formed through a solid block of thermally insulativematerial, e.g., alumina. In this way, the samples and sensors arethermally decoupled, allowing greater flexibility in the type ofsorption tests performed by gas sorption apparatus 100.

Switchable manifold 101 also includes one or more very low-displacementvalves, such as such as rotating valves and/or sliding valves, forfluidly coupling and decoupling sensors 102A-D from samples 103A-D,respectively as well as for fluidly coupling sensors 102A-D from samples103A-D from dosing gas source 104 or vacuum source 105. Verylow-displacement valves are known in the art, and are well suited forapplications in which conduits formed through a solid material need tobe sealed. For example, a very low-displacement valve or valves may beincorporated into the body of the Switchable manifold 101 as a system ofrotating or sliding plates with fluid coupling holes and grooves betweensealing gaskets. In addition, use of very low-displacement valves maysubstantially reduce error in pressure- and volume-dependentmeasurements, such as PCT measurements. An example of the mechanicalorganization and operation of a sliding valve 406 is described below inconjunction with FIG. 4A.

Array 102 includes a plurality of sensors 102A-D, each of which isfluidly coupled to a single low-volume conduit 106. Sensors 102A-D maybe individually positioned in fluid contact with low-volume conduits106, as shown in FIG. 1. Alternatively, sensors 102A-D may be configuredas a single assembly or sensor array, as described below in conjunctionwith FIGS. 5-7. It is contemplated that sensors 102A-D may be selectedfrom a wide variety of possible sensor types, depending on theparticular dosing gas used and specific test being performed. Sensorsthat may be used in array 102 include pressure transducers andconventional gas detectors. In one embodiment, when the dosing gas is ahydrogen-containing gas, array 102 may include hydride-based sensors,which contain a material that forms an optically and/or electricallyresponsive hydride upon exposure to hydrogen-containing gas. Forclarity, gas sorption apparatus 100 is illustrated in FIG. 1 with onlyfour sensors 102A-D, and array 102 is depicted as a linear array.However, embodiments of the invention contemplate array 102 containing alarge number of sensors, e.g., 10s or 100s of sensors. Further, thesensors making up array 102 may be arranged in a two-dimensional array,as illustrated below in FIG. 8, the two-dimensional array having a meansto fluidly separate each detector one-from-another. The sensors orsensor arrays may be replaceable to allow sensor types to be changeddepending on the experimental conditions, or easily replaced whencontaminated or not functioning.

As noted above, sensors A-D of array 102 may be pressure transducers,which are high-accuracy pressure measuring device capable of detectingchanges in relative or absolute pressure in each of low-volume conduits106 to the degree necessary for performing gas sorption tests. Forexample, types of pressure transducers suitable for use in array 102include a strain-gauge pressure transducer, a piezoelectric pressuretransducer, or a capacitance manometer, such as a Model 870BMicro-Baratron® or chip-based micro-pressure-sensors. In one embodiment,each sensor in array 102 may include an array of multiple pressuretransducers, each having a different operating pressure range.

When array 102 includes pressure transducers, gas sorption apparatus 100may be used as a Sievert's device to perform a PCT measurement or a TPDmeasurement of specific gases as they are absorbed or desorbed from eachof samples 103A-D. In this embodiment, each of sensors 102A-D may alsoinclude a temperature sensor. In this way, the temperature and pressureof the dosing gas being tested are both known. As noted above, duringtesting, sensors 102A-D are fluidly coupled to samples 103A-D,respectively, via low-volume conduits 106. Because the internal volumeof low-volume conduits 106 is a small and accurately known volume, thepressure changes that occur in the volume between sensors 102A-D andsamples 103 due to sorption or desorption of a dosing gas arecompounded. Therefore, the mass of dosing gas that flows into or out ofeach material sample can be very accurately determined.

Array 102 may include conventional gas sensors known in the art, such asflammable gas detectors or other gas sensors. In this embodiment,sensors 102A-D may be used to quantify the amount of dosing gas releasedfrom or absorbed by samples 103A-D based on a property change of areactive material contained in the sensor, such as resistivity change.Because the resistivity of the reactive material may be function of howmuch dosing gas is present, the quantity of desorbed dosing gas iseasily measured. Alternatively, array 102 may include fuel cell-basedsensors, which are designed to produce a voltage upon reaction with adosing gas, particularly hydrogen-containing gases. In yet anotheralternative embodiment, array 102 may include thermal conductivity orgas resistivity sensors that measure the density of gas within thelow-volume conduits 106. It is noted that the accuracy of measurementsbased on sensor reaction with the dosing gas may be enhanced by theconfiguration of gas sorption apparatus 100 since the internal volume oflow-volume conduits 106 is a small, known volume. An exemplaryembodiment of a sensor using an electrically responsive material isdescribed below in conjunction with FIG. 5.

In one embodiment, array 102 may include hydride-based sensors, whichcontain a material that forms an optically and/or electricallyresponsive hydride upon exposure to hydrogen-containing gas.Hydride-forming materials, as defined herein, include any material thatchanges physical properties on contact with hydrogen, and is not meantto necessarily imply the formation of a stoichiometric hydride compound.Hydride-forming materials that may be used in hydride-based sensorsinclude yttrium (Y), lanthanum (La), magnesium-titanium (Mg—Ti) alloys,magnesium-nickel (Mg—Ni) alloys, and various palladium (Pa) alloys. Infact, most hydrides undergo some optical transformations and/orelectrical property changes during formation from a non-hydridedmaterial. Therefore, many other possible hydride-forming materials mayalso be used to some effect in such sensors. Again, the low internalvolume of low-volume conduits 106 is beneficial for improved accuracy ofmeasurements. An exemplary implementation of an optically responsivehydride-based sensor is described below in conjunction with FIGS. 6 and7.

Yttrium is one example of an optically responsive material that may beused in a hydride-based sensor, according to an embodiment of theinvention. Yttrium is highly reflective at visible wavelengths, andforms hydrides (YH₂ and YH₃) that each have different reflectivities.YH₂ is slightly less reflective than yttrium, and YH₃ is nearlytransparent. Therefore, when hydrogen gas is brought in contact withyttrium, an optical detector will register less light reflected from thesurface of the yttrium as more hydrogen is absorbed by the yttrium. Acorrelation between the quantity of hydrogen gas absorbed and theintensity of light registered by the optical detector can beconstructed, so that the reflectance of the sensor indicates thequantity of gas that has been absorbed by the detector and, therefore,released by the sample. Such processes are most advantageous when thedetector material is reversible under typical operating conditions,however it is contemplated that one-time-use only detectors may be used.Some materials, such as yttrium, may require an active, gas-transparentcoating, such as a palladium cap to prevent oxidation of the yttrium andpossibly also act as a catalyst for dissociation of the active gas suchas hydrogen.

Each of samples 103A-D includes a material sample prepared for sorptiontesting. Hence, each material sample is isolated from the ambientenvironment in an gas-tight fashion and held in a small-volume chamber.Each material sample may be a thin-film material deposited on asubstrate, a bulk sample, or any other morphology conducive to sorptiontesting, such as a bulk sample that has been pulverized. In oneembodiment, a filter may be disposed between each sample and thelow-volume conduit 106 fluidly coupled thereto, to prevent contaminationand fouling of the low-volume conduit 106 by the sample material. Asdescribed above regarding sensors 102A-D, each of samples 103A-D may beindividually positioned in fluid contact with low-volume conduits 106,as shown in FIG. 1. Alternatively, samples 103A-D may be configured as asingle assembly, such as a sample library. Sample libraries, accordingto embodiments of the invention, are described below in conjunction withFIG. 3.

Valve controller 111 operates pressure controller 112 and the verylow-displacement valves contained in switchable manifold 101, therebyestablishing the connections between dosing gas source 104, vacuumsource 105, samples 103A-D, and sensors 102A-D. Pressure controller 112controls the pressure of gas introduced into switchable manifold 101from dosing gas source 104, which is beneficial for certain sorptionmeasurements. The control valve may consist of a manual orsoftware-controlled pressure regulator, a flow control device, or needlevalve. Temperature controller 113 controls the individual heaters 116that make up heater assembly 115, to maintain each of samples 103A-D andsensors 102A-D at a prescribed temperature or temperature history, suchas a controlled temperature ramping rate. As shown in FIG. 1, anindividual heater 116 may be positioned in proximity to each of samples103A-D and/or sensors 102A-D. Controlling the sample and detectortemperature aids in performing certain sorption measurements. Datacollection system 114 is configured to obtain information from each ofsensors 102A-D. The information may be obtained, for example, by anelectrical connection, an optical connection, or though an opticalsystem that images the sensors.

In operation, gas sorption apparatus 100 is configured to perform one ormore sorption tests simultaneously on a plurality of samples. Dependingon the type of sensors in array 102, gas sorption apparatus 100 mayperform PCT and TPD tests on samples 103A-D and generate kinetic andthermodynamic stability information about the samples. In the course ofsuch testing, switchable manifold 101 fluidly couples samples 103A-Dand/or sensors 102A-D, to dosing gas source 104, and to vacuum source105, as well as to each other. FIGS. 2A-G schematically illustratevarious operations performed by gas sorption apparatus 100 in the courseof such sorption testing, according to different embodiments of theinvention.

FIG. 2A schematically illustrates gas sorption apparatus 100 withswitchable manifold 101 positioned to fluidly couple samples 103A-D andsensors 102A-D to vacuum source 105 for evacuation of any gasescontained therein. Evacuation may be performed as part of a preparationprocess for testing of samples 103A-D. FIG. 2B schematically illustratesgas sorption apparatus 100 with switchable manifold 101 disposed tofluidly couple samples 103A-D to dosing gas source 104 for fullycharging samples 103A-D and sensors 102A-D in preparation for desorptionPCT dosing measurements. FIG. 2C schematically illustrates gas sorptionapparatus 100 with switchable manifold 101 positioned to fluidly coupleeach of samples 103A-D to a corresponding sensor 102A, 102B, 102C, or102D. In this configuration, each of sensors 102A-D are in direct “gascontact” to a corresponding sample by means of a fluid path that hasvery little, if any, free volume, i.e., a low-volume conduit 106. FIG.2D schematically illustrates gas sorption apparatus 100 with switchablemanifold 101 positioned to fluidly couple each of sensors 102A-D tovacuum source 105, to pump-down sensors 102A-D. FIG. 2E schematicallyillustrates gas sorption apparatus 100 with switchable manifold 101positioned to fluidly couple each of samples 103A-D to vacuum source105, to pump-down samples 103A-D. FIG. 2F schematically illustrates gassorption apparatus 100 with switchable manifold 101 positioned tofluidly couple each of sensors 102A-D to dosing gas source 104, tocharge sensors 102A-D with a dosing gas. FIG. 2G schematicallyillustrates gas sorption apparatus 100 with switchable manifold 101positioned to fluidly couple each of samples 103A-D to dosing gas source104, to charge samples 103A-D with a dosing gas.

In FIGS. 2A-G, the fluid coupling and decoupling of sensors 102A-D andsamples 103A-D to dosing gas source 104, vacuum source 105, as well asto each other, are shown schematically. One skilled in the art willreadily understand how to configure low-volume conduits 106 and slidingand/or rotating valves to allow such fluid coupling to take place, as isdescribed herein. Further, while fluidly coupling samples 103A-D orsensors 102A-D to dosing gas source 104, vacuum source 105, and/or toeach other, simultaneously may be advantageous, individually controllingthe fluid coupling of each of samples 103A-D and/or sensors 102A-D byswitchable manifold 101 also falls within the scope of the presentinvention. Although more complex, one of skill in the art will readilyunderstand how to configure a system of sliding and/or rotating valvesthat allows such individual connection of samples 103A-D or sensors102A-D, as needed.

By way of example, an absorption PCT measurement procedure is describedwith respect to the different configurations of gas sorption apparatus100 illustrated in FIGS. 2A-G. First, sensors 102A-D and samples 103A-Dare evacuated, as shown in FIG. 2A. Next, samples 103A-D are isolatedand dosing gas is introduced to sensors 102A-D, as illustrated in FIG.2F. Sensors 102A-D are then fluidly coupled to samples 103A-D asillustrated in FIG. 2C, and the change in gas concentration in each ofsensors 102A-D and corresponding low-volume conduits 106 is measured aseach of samples 103A-D absorb the dosing gas. The quantity of gas changein each of sensors 102A-D and low-volume conduits 106 is used tocalculate the quantity of gas absorbed by each of samples 103A-D, and apoint on the PCT curve for each sample is plotted. This procedure isthen repeated at increasingly higher pressures to generate additionalpoints and thereby construct a full PCT curve for each of samples103A-D. Desorption PCT curves may be performed in the same manner,except that one would start by fully charging the sample and detectorsat the highest pressure by exposing both samples 103A-D and sensors102A-D to the gas source at highest pressure and then dosing gas out ofeach sample by decreasing the pressure in the sensor and conduit insteps as above.

It is noted that in principal one would really need each of sensors102A-D to be pressure sensors rather than concentration sensors toconstruct true equilibrium PCT curves, since the final equilibriumpressure should be known at each dose and because concentration can bedetermined in the classic Sieverts method by knowing the volume, gastemperature and pressure change. Due to the difficulty in making anarray of highly accurate, separate pressure sensors, it is contemplatedthat, in one embodiment, gas sorption apparatus 100 may perform suchmeasurements in an easier but less accurate way. To wit, a concentrationsensor, such as the metal-hydride optical sensors described below inconjunction with FIGS. 6 and 7, measures only the concentration changewith each dose. This concentration change may be plotted versus theapplied dosing pressure, which may be taken from a single pressuresensor at the dosing gas supply line. In this way the storage capacityof each of samples 102A-D is quantified and an approximate PCT plotconstructed. By taking very regular steps in dosing gas pressure, or atleast knowing the difference in source pressure between steps andmeasuring the concentration change, it is possible to back calculate theequilibrium pressure for each sample to construct the true PCT curve.

Kinetics and TPD measurements can also be performed by gas sorptionapparatus 100, by configuring gas sorption apparatus 100 as illustratedin FIGS. 2A-G. Since such measurements are concentration vs. time andconcentration vs. temperature, it is not necessary to have individualpressure sensors for each sample for these measurements.

In one embodiment, samples 103A-D are arranged in a sample library,which is positioned in fluid contact with low-volume conduits 106 priorto sorption testing. FIG. 3 is a schematic illustration of a samplelibrary 300, according to an embodiment of the invention. Sample libraryincludes a plurality of sample areas s, each surrounded by a border b.Sample areas s are discretized regions on the surface of a substrate,such as a glass substrate, metal substrate, or silicon wafer. Each ofsample areas s may include a different material composition. Theplurality of material compositions contained in sample library 300 maybe formed thereon by any known combinatorial techniques or othertechnically feasible approaches including discrete or continuousdeposition techniques. For example, a continuous spectrum of materialcompositions of continuously varying mixtures may be formed over thesubstrate of sample library 300 using co-deposition of differentmaterials on the substrate. The sample areas s then discretize thecontinuously varying mixtures on the substrate, dividing the substrateinto small areas of approximately constant composition. In this way, alarge number of samples of different compositions can be quicklyprepared and simultaneously measured using gas sorption apparatus 100.In one embodiment, one or more sample areas s in sample library 300contain material compositions of known sorption properties, to be usedfor reference or calibration purposes.

The size of each sample area s may be relatively small, so that a largenumber of different material compositions, e.g., 10s or 100s, can becontained in a single sample library and tested simultaneously by gassorption apparatus 100. The minimum area of each sample area s is onlylimited by the practical limitations of the minimum width of border band the accuracy desired for a given sorption test. Since smaller sampleareas s are capable of absorbing and desorbing less total gas, theaccuracy of any sorption test can be adversely affected as the area ofeach sample area s is reduced and as the thickness of each sample area sis reduced.

The material of border b is selected to form a gas or liquid barrierbetween the samples, so that each sample area s may be completelyisolated from adjacent sample areas during sorption testing. In oneembodiment, border b is simply a region of sample library 300 in whichno sample material has been deposited. In another embodiment, border bincludes an isolation member. The isolation member may be a raisedsealing material used to establish a gas-tight seal with low-volumeconduits 106. In this embodiment, the surface of switchable manifold 101may be a smooth, polished surface against which the isolation member ispressed, thereby isolating each sample area s from adjacent sample areaswhile fluidly coupling each sample area s to a corresponding low-volumeconduit 106.

Because the quantities of gas that are sorbed and desorbed fromthin-film samples are extremely small, even a small quantity of gasoutgassing from the isolation member can adversely affect the accuracyof a sorption test. Consequently, it is contemplated that the isolationmember may be formed from a material that is subject to essentially nooutgassing or gas permeability over the wide range of temperatures andpressures associated with sorption tests. Many UHV-compatible materialsmay be used for this purpose and are well-known, such as a O-rings orUHV high-temperature epoxy. In another example, the isolation member maybe a grid deposited in border s, the grid being formed from a relativelysoft metal, such as nickel or copper. In another embodiment, theisolation member is incorporated into a surface of switchable manifold101, as described below in conjunction with FIGS. 4A, B.

FIGS. 4A, B illustrate schematic side views of one embodiment of theisolation of each sample area s of sample library 300 from adjacentsample areas. In FIG. 4A, sample library 300 is positioned proximate toa sample receiver 402 in preparation for mounting thereon. In FIG. 4B,sample library 300 is shown mounted on sample receiver 402 and ready forsorption testing by gas sorption apparatus 100. In this embodiment, eachsample area s is fluidly coupled to a dedicated low-volume conduit 106,and is fluidly isolated from adjacent sample areas s when sample library300 is mounted on sample receiver 402. Sample receiver 402 is configuredwith an array of knife edges 401 that are aligned with isolation members405, which are disposed on sample library 300. In this embodiment,isolation members 405 may be formed from a relatively soft material,such as copper, nickel, or a UHV-compatible polymer, and knife edges 401may be a relatively hard material, such as stainless steel. Thus, whensample library 300 is mounted on sample receiver 402, knife edges 401engage with isolation members 405 to fluidly isolate each of sampleareas s. Alternatively, sample receiver 402 may not be configured withknife edges 401 and instead engages isolation members 405 with asubstantially flat, polished surface to form the gas-tight seal. Inanother alternative embodiment, the surface of switchable manifold 101may consist of an array of isolating rings, or squares of knife-edgeraised material that press into isolation members 405, thereby isolatingeach sample area s from adjacent sample areas while fluidly couplingeach sample area s to a corresponding low-volume conduit 106. In yetanother embodiment, the entire substrate of the sample library 300 iscomposed of material softer than the knife-edge material 401, such thatthe knife-edge material is pressed into the substrate between thediscretized sample areas s or through a non-discretized continuoussample s, thereby isolating each sample area s from adjacent sampleareas while fluidly coupling each sample area s to a correspondinglow-volume conduit 106. Sample receiver 402 also includes low-volumeconduits 106 positioned between knife edges 401, and is fluidly coupledand decoupled from switchable manifold 101 by a sliding valve 406.Sliding valve 406 actuates to fluidly couple and decouple samplereceiver 402 and any sample library mounted thereon by translatinghorizontally as indicated by arrow 407.

In one embodiment, array 102 in FIG. 1 includes sensors with anelectrically responsive material to quantify the quantity of gasreleased from sample materials during sorption testing. As noted above,such sensors may include hydride-based sensors or more conventional gasdetectors. In either case, exposure to and reaction with the dosing gascauses the electrically responsive material contained in the sensor toundergo a change in one or more electrical properties, such asresistivity or electrochemical potential. This change in electricalproperties can then be used to quantify either the amount of dosing gasthat has reacted with the electrically responsive material, or theconcentration of dosing gas that is in fluid contact with theelectrically responsive material. In either case, the quantity of gasreleased by a sample can be easily calculated.

FIG. 5 is a schematic side view of a sensor array 500 containing anelectrically responsive material 501, according to an embodiment of theinvention. Sensor array 500 is one embodiment of array 102, and includesa plurality of sensors d, which are each fluidly coupled to acorresponding sample (not shown) via low-volume conduits 106 and asliding valve 406. Each sensor d has a conductor that provides a signalback to data collection system 114.

In one embodiment, array 102 in FIG. 1 includes sensors with anoptically responsive material to quantify the quantity of gas releasedfrom samples material during sorption testing. As noted above, suchsensors may include hydride-based sensors, where exposure to andreaction with hydrogen gas causes the optically responsive materialcontained in the sensor to undergo a change in one or more opticalproperties, such as reflectivity and/or transmissivity of visible light.

FIG. 6 is a schematic side view of a sensor array 600 containing anoptically responsive material 601, according to an embodiment of theinvention. Sensor array 600 is one embodiment of array 102, and includesa plurality of sensors 602, which are each fluidly coupled to acorresponding sample (not shown) via low-volume conduits 106 and asliding valve 406. In operation, illumination 605 from a light source isdirected on sensors 602, and light 606 reflected from sensors 602 iscollected by an optical detector 608. Optical detector 608 may be adigital camera that captures the condition of multiple sensors 602 withone or more images. The images are then stored in and/or processed bydata collection system 114 in FIG. 1. Alternatively, optical detector608 may include a plurality of light sensors, such as photocells, sothat each sensor 602 has a corresponding and dedicated light sensor.Thus, the optical response from each sensor may be gathered eithersimultaneously or individually. As noted above, exposure to the dosinggas produces a change in the reflectivity and/or transmissivity of theoptically responsive material, which is measured by optical detector 608or detectors as described herein.

FIG. 7 is a schematic side view of a sensor that includes an opticallyresponsive material 701 and may be included in array 102, according toan alternative embodiment of the invention. Similar to sensors 602,exposure of dosing gas to sensor 700 produces an optical response inoptically responsive material 701 that can be detected and/or recordedby an optical detector. In sensor 700, however, optically responsivematerial 701 undergoes a distinct color, transparency and/orreflectivity change upon absorption of the dosing gas, rather than agradual change in reflectivity or transmissivity as more dosing gas isabsorbed. In this fashion, a clearly defined region of opticallyresponsive material 701 changes color when sensor 700 is exposed to adosing gas of the appropriate chemistry. For example, when the dosinggas being measured by sensor 700 is hydrogen, optically responsivematerial 701 may be a yttrium- or lanthanum-based compound. As is knownin the art, such compounds can produce the distinct reflectivity changenecessary for sensor 700 to function as contemplated herein.

To isolate optically responsive material 701 from ambient hydrogen andother contamination that may result in unwanted optical changes orpassivation, sensor 700 includes a protective layer 705 that isolatesoptically responsive material 701. Layer 705 may be the nativeyttrium-oxide or a secondary deposited metal oxide or impermeable metalor polymer layer, which is known to prevent diffusion of hydrogentherethrough. Sensor 700 also includes a palladium orifice or window 702deposited in and sealing opening 707 of protective layer 705, as shown.Thus, palladium orifice 702 prevents fluid contact between gases presentin low-volume conduit 106 and optically responsive material 701preventing oxidation or passivation of the responsive material 701 insealing opening 707. However, since hydrogen readily diffuses throughpalladium, optically responsive material 701 should only be exposed tohydrogen that is introduced via low-volume conduit 106 and the palladiumorifice 702. Sensor 700 responds to exposure to hydrogen by forming acircular reacted region of different color, transparency, orreflectivity centered over opening 707, where the diameter of thereacted region can be readily correlated to a quantity of hydrogen gasabsorbed by sensor 700. The diameter of the reacted region in sensor 700and the diameters of the reacted regions in all other sensors in thesame sample library can then be recorded simultaneously by an opticaldetector, such as a digital camera. In this fashion, hydrogen releasedby a plurality of samples in sample library 300 can be simultaneouslyquantified, greatly speeding the screening process.

FIG. 8 illustrates a schematic top view of a sensor array 800 containinga plurality of sensors 700 after sorption testing. As shown, circularregions 801 are visible and the diameters thereof are easily measured.Thus, desorbed gas concentrations of each sample may be correlated togas over-pressure and temperature of each sample in a single or seriesof measurements.

In an alternative embodiment, the sensor array 800 may be pre-chargedwith gas to the fully absorbed state and then exposed to the samplearray with each sensor acting as a gas source. The concentration of gasabsorbed by each sample can be measured quantitatively by the diameterof the desorbed circular regions 801 of the sensor array 800.Additionally, measured increases (sample desorption) or decreases(sample absorption) of the diameter of the circular regions 801 withtime may provide a measurement of the individual kinetics of gasdesorption or sorption of the array of samples at a given temperature orwith a controlled temperature ramping.

In one embodiment, a sensor array containing sensors d in FIG. 5,sensors 602 in FIG. 6, and/or sensor 700 in FIG. 7 may be formed on asilicon substrate or an optically transparent substrate such as glass.Deposition and etching processing techniques are well suited toefficiently fabricating a large number of very small sensors on a singlesubstrate, thereby facilitating the screening of large numbers ofdifferent material compositions. Sensors containing either electricallyand/or optically responsive material, can be formed in this manner.

In one embodiment, a sensor array, such as sensor array 102, may bemounted to switchable manifold 101 in FIG. 1 using the same techniquesdescribed above for sample library 300, so that each sensor is fluidlyisolated from each adjacent sensor, but is fluidly coupled to acorresponding sample material.

In one embodiment, hydride-based sensors may be used as mini-reservoirsof hydrogen gas and can therefore be used as “mini-dosers.” For example,sensor array 800 can be dosed with hydrogen such that each sensor 700contains a known quantity of hydrogen gas. Sample materials in a samplelibrary can then be fluidly coupled to vacuum source 105 of FIG. 1and/or heated, as necessary, to release the hydrogen or contaminantscontained in each sample material. Sensors 700 are fluidly coupled tothe sample library and heated, as required, to release hydrogentherefrom. Sorption of hydrogen into each sample can then be readilyquantified by comparing the quantity of hydrogen actually released byeach sensor 700. Because the hydrogen content of each sensor 700 ismeasured optically, which, again, can be done quickly and accurately,measurements of the hydrogen content of the sensors 700 can be performedmultiple times throughout the life of a given test. This approach allowsthe simultaneous collection of kinetic and thermodynamic stabilityinformation for a large number of material samples simultaneously. Inone embodiment, one or more of the samples so tested may be a controlsample, comprising a material that is known to absorb no hydrogen. Suchcontrol samples may be used to assist in the calibration of sorptiontests by quantifying how much hydrogen is present in a low-volumeconduit 106 at a specific pressure and temperature and at any timeduring the sorption test.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A gas sensing system, comprising: a hydride-forming material; anoptical sensor directed at the hydride-forming material; a fluid conduitconfigured to transport a test gas to the hydride-forming material; anda palladium orifice configured to fluidly isolate the hydride-formingmaterial from the fluid conduit, wherein the optical sensor isconfigured to detect a change in the hydride-forming material uponexposure to the test gas.
 2. The gas sensing system of claim 1, whereinthe hydride-forming material comprises a material selected from thegroup consisting of yttrium (Y), lanthanum (La), magnesium-titanium(Mg—Ti), magnesium-nickel (Mg—Ni), and palladium (Pa).
 3. The gassensing system of claim 1, the hydride-forming material is disposedwithin a sample library.
 4. The gas sensing system of claim 3, whereinthe sample library comprises an optically transparent substrate.
 5. Thegas sensing system of claim 3, further comprising: a second fluidconduit configured to transport the test gas to the hydride-formingmaterial; and a second palladium orifice configured to fluidly isolatethe hydride-forming material from the second fluid conduit.
 6. The gassensing system of claim 5, further comprising a switchable manifoldfluidly coupled to the first and second fluid conduits.
 7. The gassensing system of claim 1, wherein the hydride-forming materialcomprises a material that is optically responsive in the presence ofhydrogen.
 8. A gas sensing system, comprising: a hydride-formingmaterial configured to form at least one sensor; a first fluid conduitconfigured to fluidly couple the hydride-forming material to a firstsample; and a second fluid conduit configured to fluidly couple thehydride-forming material to a second sample, wherein the first andsecond fluid conduits have an inner diameter no greater than 2 mm. 9.The gas sensing system of claim 8, further comprising a switchablemanifold fluidly coupled to the first and second fluid conduits.
 10. Thegas sensing system of claim 9, wherein the switchable manifold isconfigured to fluidly couple the first conduit to a first sample and thesecond fluid conduit to a second sample.
 11. The gas sensing system ofclaim 9, wherein the switchable manifold is configured to fluidly couplethe first and second conduits to the hydride-forming material.
 12. Thegas sensing system of claim 9, wherein the switchable manifold isconfigured to fluidly couple the first and second fluid conduits to adosing gas source.
 13. The gas sensing system of claim 9, wherein theswitchable manifold is configured to fluidly couple the first and secondfluid conduits to a vacuum source.
 14. The gas sensing system of claim9, wherein a portion of each of the first and second fluid conduitscomprises holes formed in a body portion of the switchable manifold. 14.The gas sensing system of claim 8, wherein the hydride-forming materialcomprises a material that is optically responsive in the presence of adosing gas.
 15. The gas sensing system of claim 15, further comprisingan optical sensor directed at the hydride-forming material.
 16. The gassensing system of claim 15, wherein the dosing gas is hydrogen.
 17. Thegas sensing system of claim 8, wherein the hydride-forming materialcomprises a material that is electrically responsive in the presence ofa dosing gas.
 18. The gas sensing system of claim 18, further comprisinga conductor electrically coupling the material to a data collectionsystem.
 20. The gas sensing system of claim 8, wherein thehydride-forming material is deposited on a substrate.
 21. The gassensing system of claim 8, wherein the hydride-forming material forms atleast two sensors, wherein a first sensor is fluidly coupled to thefirst sample via the first fluid conduit, and a second sensor is fluidlycoupled to the second sample via the second fluid conduit.